To debug the URL Rewrite module, you can use the IIS 7.x "Failed Request Tracing," which, contrary to its name, can be used to trace successful as well as failed requests. This learn.iis.net page illustrates how to configure this and amount of detailed debugging information that is available. You don't need to create a test page as suggested in the blog entry--- just jump to the "Configure Failed Request Tracing" section.